Cell death is widespread during the development of the nervous system, where it helps to ensure that the proper number and types of connections are formed between neurons and their targets. During development, cell death occurs when neurons fail to receive adequate survival signals from trophic factors such as nerve growth factor (NGF). Accumulating evidence suggests that trophic factor deprivation-induced death also contributes to human neuronal disorders and degenerative diseases. We previously identified the prolyl hydroxylase EGLN3 as a mediator of NGF deprivation-induced cell death. EGLN3 is one of a small family of prolyl hydroxylases that function key as oxygen-dependent regulators of the transcription factor hypoxia- inducible factor (HIF). Besides regulating HIF, recent reports suggest that EGLNs have HIF-independent functions. We have obtained preliminary evidence for a novel interaction between EGLN3 and the pro- apoptotic Bcl-2 family protein BIM(EL). Moreover, we have found that EGLN3 and BIM(EL) each interact with the von Hippel-Lindau protein (pVHL), a subunit of the E3 ubiquitin ligase that targets HIF for degradation. Here we will test the hypothesis that EGLN3, pVHL, and BIM(EL) function coordinately to regulate trophic factor deprivation-induced cell death. In Aim 1 we will determine the functional relationship between EGLN3 and BIM(EL) during NGF deprivation-induced cell death using a combination of over-expression and gene knock-out and knock-down approaches. Aim 2 addresses the biochemical significance of the EGLN3/BIM(EL) interaction. Experiments will characterize how the interaction between EGLN3 and BIM(EL) influences the pro- apoptotic function of BIM(EL) and/or the prolyl hydroxylase activity of EGLN3. In Aim 3, we will determine how pVHL regulates EGLN3 and BIM(EL) expression and function. We will also test our hypothesis that pVHL plays a pro-apoptotic role in trophic factor deprivation-induced cell death. These studies should further our understanding of the mechanisms that lead to neuronal death during development, and in nervous systems disorders such as stroke, spinal cord injury, and other neurodegenerative conditions in which trophic factor deprivation contributes to the loss of neurons.Neurotrophic factor deprivation contributes to the loss and dysfunction of neurons in human brain diseases and disorders such as stroke, spinal cord injury, peripheral neuropathy, and neurodegenerative disease. This project will characterize new mechanisms that regulate cell death caused by neurotrophic factor deprivation. Information gained from this project may help identify new targets for therapies aimed at preventing neuronal loss. Neurotrophic factor deprivation contributes to the loss and dysfunction of neurons in human brain diseases and disorders such as stroke, spinal cord injury, peripheral neuropathy, and neurodegenerative disease. This project will characterize new mechanisms that regulate cell death caused by neurotrophic factor deprivation. Information gained from this project may help identify new targets for therapies aimed at preventing neuronal loss.